radar

Everyday

1. Radar is a system that sends out radio waves and catches them when they bounce back, to find where planes, ships, storms or cars are and how fast they move. tree →
2. «On someone's radar» means they know about it or are paying attention to it. tree →

In the lessons

In science radar shows how waves reflect; weather radar maps show rain clouds; police use radar to catch speeding cars; airports use it to guide planes. Bats and dolphins use a similar idea with sound (echolocation). Phrases: «on the radar», «under the radar», «weather radar», «radar screen».

Examples

• Air traffic controllers watch planes on the radar. tree →
• The weather radar shows rain coming this afternoon. tree →
• The police used radar to check the cars' speed. tree →
• The ship's radar spotted an iceberg. tree →
• Bats find insects in a way a bit like radar, using sound. tree →
• The test is not on my radar yet — when is it? tree →

Note

Usually uncountable («radar»), sometimes «a radar» for one machine. It reads the same backwards: r-a-d-a-r (a palindrome). It was first a short form of «RAdio Detection And Ranging». «Under the radar» means not noticed.